Ok, so before the flames start, let me get this out of the way. I am completely aware of all risks associated with wakesurfing, and how those risks increase substantially when not behind an inboard boat. My purpose of this thread is for reasearch purposes to help weigh my decision to proceed or not.
I currently use our family I/O for skiing and wakeboarding. I wakesurf behind friends' Direct drives and V-Drives. The problem is sometimes coordinating times to get out. I would love to be able to wakesurf behind our own boat. Selling it and buying a inboard or straight up buying an inboard is not an option right now due to finances and the fact that we own the boat clean and clear and have for 20+ years. It is the boat all my family has grown up with and has too much sentimental value to simply get rid of for something else. Not to mention it still runs great and is economical to use.
It is a 1973 Marlin sports boat. It seats about 7 with wrap around seating. It is a closed bow and has a 302 in it with an Alpha One outdrive.
We have modified it so far with a custom transom pylon for wakeboarding. Without any ballast whatsoever it throws a fairly decent wakeboard wake, enough to get a few feet of air and do wake to wakes.
I am contemplating making a custom swim platform, currently it has none, just a little boarding ladder off to one side of the transom.
I have made a custom surf platform for my friend's Supra that works well and is about 2 feet long from transom to tip. I am familiar with what would need to be done to make one for the I/O.
My thought is to make a platform that goes from just inside tie down hooks on the transom and extends out in a squished hexagon shape about 3 feet from the transom. This would definitely cover the outdirve. I would need to make a cutout in the middle of it from the transom to allow the outdrive to be raised when trailering.
The platform I made is this one:
It would be similar to this, but wider from transom to the end and have a cutout in the middle for the outdrive. The transom of the I/O is here:
I also would be putting on a prop guard similar to this one
which would eliminate the possibility of any hands, feet, rope, etc. from ever being caught in the prop.
Doing both of these should/would eliminate any of the hazards of surfing behind an I/O. It would not only cover the prop, so if you did fall towards the boat, you would fall into the platform, like on an inboard. Also behind the boat, the prop and outdrive would be covered, so if you fell so close to the boat you were under the platform (not very likely) you would not have the prop to worry about.
My first question is, does this seem logical and feasible? Do you think this would be safe enough?
My second question is, with such a big platform, does it seem like it would mess up the surf wake? I know sometimes a platform can dig into the wake and act as a trim tab, and messes the wake up more if it has a lip. This would be flat and have no lip, allowing the water to flow under it smoothly. I'm thinking this has more of an effect on the wake than the sides of it being in the water.
More than likely there would be at least 1 750lb sack on the rear corner seat and possibly more on te rear seat.
My third question is, if all these modifications were done to make it safe, and it produced a decent surf wake, would you surf behind it?

Once again, no flames, I know surfing behind an I/O is a bad idea, but with these modifications to it, could it be something that would be about as safe and enjoyable as an inboard?

Also I plan on taking the boat out without platform, guard, or any boards for that matter and sacking it up to see if it can make a decent surf wave in the first place before any of this. I guess that will be the factor on if the idea would be scrapped at all. No use in doing all this if it can't be surfed behind anyway.

Not completely safe, but totally doable. If I trusted my driver, I would do it no problem. A quick search of the internet will yield hundreds of photos of people surfing behind I/Os and outboards (without a rope). My dad and even my great uncle used to do it all of the time on an old 9ft waterlogged board in the 60s-70s. A proper ocean board would give you a little more distance from the prop and safety.

That prop guard can still allow hands and feet in it. Besides that, just running into the outdrive assy could cause serious injury.

Sorry..... plain and simple- This is a very bad idea.

I know that prop guard would, that one is just for illustration. I have a friend with a machine shop. IF I were to do something like this, it would be made with a very skinny waffle pattern all around with about 1/4" holes all around.

The outdrive assembly would be covered, that is what the extended platform's purpose would be.

Here is a quick paint sketch of what I'm thinking of. With this, in order to hit any of outdrive assembly you would have to fall forward a good foot and fall straight down about 3-4 feet underneath the platform to hit any part of the assembly.
How many people here have ever fallen underneath the platform while surfing? Show of hands?

From what I'm reading, your concerned about the propeller injuring someone while reboarding the boat.
If this is the case, this would happen the same way as wakeboarding or skiing. We always kill the engine when someone is getting close to the boat or is getting in or out even when we're behind the inboards doing anything. Also as I said, the prop guard would have 1/4" maximum size holes all around and be impossible to get even a finger in.

There have been lots of threads on this, but I haven't heard of any actual injuries that have come from the concerns we're all worried about. Yes, there is the one pic of the mangled hand that I've seen, but there was no proof that it actually came from surfing or how it really happened.

That said, let's set the safety concerns aside and talk about platform.

1) If you had a long enough platform to address your safety concerns, I honestly think it might affect your ability to ride in the pocket (if you could make one). As you well know, there are times when (depending on boat/speed/ballast/etc) you're nosing up on the platform on an inboard. I would think that if you made your platform toooooo long, that it might be encroaching on your "surf zone".

2) Platform height will be somewhat important. I know when my boat is slammed, the platform is LOW in the water at rest (I can float my ass onto the platform on the surf side, LOL). Anyway, if you have the flexibility to build a platform at the appropriate height and length, it might be helpful.

And no, I've never fallen underneath my platform. I did have it happen yesterday where the boat sputtered and chopped power (water in fuel probably) and I had more than enough momentum that I had to surf around the side of the boat. I was at a point where I was almost able to reach over and grab the railing around the trunk--and that was after cutting out to make sure I was surfing around the side of the boat rather than running into the stern. It would most certainly have to be the "perfect storm" to hit an outdrive. 90% of the people here wouldn't risk it. 90% of the people here don't have to.

There have been lots of threads on this, but I haven't heard of any actual injuries that have come from the concerns we're all worried about. Yes, there is the one pic of the mangled hand that I've seen, but there was no proof that it actually came from surfing or how it really happened.
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I have heard of 2, and was actually a witness of 1....... That would be why I wouldn't even consider anything like this.

That prop guard might add the needed safety, but I think it will probably cause unwanted turbulence in the wake......

FWIW, I know the OP. He rides on my DD often. but he has a serious passion and drive to surf and has limited option as far as access to a surfable boat with his family. Like I told him, 90% of the people on here don't even need to consider an I/O because we have an inboard or access to one that fulfills out needs. Bottom line is that there's a very small slice of the population that has his passion/desire enough for it to even be a consideration... And it's a hell of a lot easier for someone like me to say "it's not worth it".

my issue would not be from the op-your friend, but more with everyone else on the lake and pics that spread to other lakes and pretty soon, i/o's are surfing everywhere with people that have no business doing it. Then the accidents start and we all know what will happen if the gov't gets involved. it'll be NO surfing anywhere behind anything and a long fight to get inboards exempted.
I think now there's enough press out there that say never do this behind an i/o or outboard and personally it should stay that way.

I can appreciate the dilemma but how many others out there want to surf and can't/don't want to afford the proper gear.

Come on guys. I know most wakesurfers are super afraid of getting hurt/taking risk of any kind, but you guys are just being silly. Not a knock to the sport--its fun. Just to some of the weenies out there.

I/O surfing = to base jumping--not hardly.

If you find a safe way to convert an I/O for surfing you will be a rich man.

I know In PA it is clearly stated that surfing is only legal behind inboards not I/O or outboard.
I guess I don't get how you are emotionally attached and can't sell the boat? Save up and by an inboard. You will be happy you did.

I think before you even can put a prop guard on, or even bolt down this platform, take your boat out with a cutout of this platform, and see it in actions. Weight the boat the way you would for surfing, and (I'm guessing) you'll encounter issues with the size of the platform necessary vs. your ability to create a wave good enough to surf. Only once you have water tested the size of platform you want to install should you consider moving forward.

That said, I;m another one for the group of people who would discourage this. There HAS to be a better way of going about this than just modifying your I/O to suit a specific need. Better off finding an older DD (if money is the issue)

Might want to take a look at Tige's relatively new convex surf thing that fits under their platform and shapes the wake. That way if your platform did drag, it would be dragging in a way that was beneficial.

One year at the boat show, Chaparral was advertising one of their IO boats as being a surfable boat. Not sure if they did that for more than a year. Seemed amazingly crazy at the time.

Surf wakes are pretty finicky and people are reporting different results just from changing prop pitch. Not sure what a prop guard would do.

Given the risks, I would spend the time searching for a cheap used vdrive instead.

Been slammed at work, so just now checking back in.
1: The boat is our family boat, aka all of my immediate family has use of it whenever we want to. It is one my parents bought when it was nearly new and we have all worked on it to modify it and maintain it over the years. All my sisters grew out of the whole boating thing and really don't care much and haven't even looked it, let alone been out on it in years. This basically leaves joint ownership of it with my parents. They are all sentimental about it because that's the boat they basically raised the family on. I'm not really sentimental about it, but they are, and it lives at their place. I don't see them ever wanting to get rid of it, especially since my dad is about 60 and still all about the slalom sets and that works well for him.
2: The boat does have a really aggressive V and can list easily with not too much weight. We have not tried weighting it with ballast yet, but plan to grab some sacks and weight it to see if it makes a decent surf wave first and see where the waterline goes to determine platform height.
Because it is about a foot shorter than a CC2001, and the fact the engine is in the rear, not the middle, I figure it will need about 750-1000lbs to produce a good wake without listing too much to swamp. If one 750 did it, it would be nice as we can fit a 750 in the engine compartment and have all the ballast we need, HIDDEN!
At that point, if it does, we will make the platform. My family wants a platform on it anyway, but they haven't thought of one this big for this purpose.
3: Before investing in having a custom prop guard made, we will test it weighted with the platform and see if the wake is still good or screwed up. If it's fine, prop guard time, if not, well we have a platform on an I/O that wasn't there and we scrap the surfing idea.
4: After all this then we will try surfing it.

The total cost of this project, besides obvious stuff like sacks, rope, and board to stay in the boat is under $500, about $300 for the platform and brackets, about $200 for the prop guard. So for those of you saying to save up for a cheaper inboard, if you can find one that is surfable for $500, I'll buy it right now.
I am saving up to buy one, but that is years down the road. This would be for use when I want to surf, and all my buddies with inboards aren't available. Also it would be good for family camping trips we go on where we spend the week on the water, to be able to surf it up instead of just the slalom and wakeboarding we normally do.

I think this would work, but obviously it needs some testing. I will post up with results as it progresses. The platform will most likely be built over the winter, the same time I am building the final version of the platform for the Supra.

UPDATE:
Not going ahead with the plan.
After going out with my dad, on the Supra and demonstrating the setup and wakesurfing we discussed the project.
The main concern isn't modifying it for safety, but rather the added wear on the drivetrain of the 1973. The other concern besides that is the fact that there isn't a ton of interior space for ballast and with how little weight the boat can safely handle, it most likely wouldn't be able to produce a good surf wave anyway.
We are going to be looking into adding a smaller fat sack, possibly under the rear center seat for wakeboarding though as he did see the benefits of the increased wakeboarding wave with lighter ballast (about 250lbs) added.
We will also be building a platform for the boat, but not one meant for surfing protection, so not nearly as big, and no prop guard.

I really love skydiving, all my buddies are into it, but there's no where to go where I live! I've been thinking and my bedroom window is 32ft off the ground... If I can rig up some kinda chute... I think it just might work!

For real though, iv'e surfed an I/O before, and like Duffy said, some can make decent rideable waves. Do I recommend it, no way man. Just bum rides as best you can for now. Odds are the wave, just won't be there anyway. That said, I admire the passion and say if it comes down to it, give that ol girl a tune up and get after it! You know the risks just like anybody else. That's how all this got where it is.

Well as I said, it's not happening on the I/O. I'll just keep getting rides off of my friends' boats to surf and just do some light mods to the I/O for better wakeboarding.
Got a boat fund setup to save and buy an inboard within a few years. By the time I have the money to be in striking distance of a decent DD (sunsport, sunsetter) at the prices are at now, the market will hopefully have come down and I'll be able to get into a V-Drive by then.
I know I could always finance one, but I'd rather not have a payment and just buy it cash out.
Until then I have a handful of friends with inboards I can surf behind. I jjust want to get something for my family, so my kids, so they can have the same experience my wife and I have had growing up on the water.

^Please read a thread before responding. This is not being done and has been axed for some while.
If you had read it, you'd realize your post is the equivalent of yelling at the neighbors to turn down the music from their party that got canceled and never happened.

^Please read a thread before responding. This is not being done and has been axed for some while.
If you had read it, you'd realize your post is the equivalent of yelling at the neighbors to turn down the music from their party that got canceled and never happened.

Thanks for voting this project down. The risk just doesn't equal the reward. Smart move.

I am as sentimental as anyone about family equipment. I have my grandfathers slalom ski and always take it along on family camping trips just to have a piece of our history with us. I get sentimentality. However, perhaps your father just needs an option that works better for everyone. I too, love to slalom. My other behind the boat passion is wake surfing. We often run the course with our boat and then switch to surfing. Now, I've spent many years skiing behind an I/O and skiing behind our Ddrive is way better. Even just recreationally, it's way better. Most people assume a Ddrive won't surf worth a chit. Most don't. Most is not the same as all.

If you could somehow talk your father into letting go of the old I/O, taking that money and pooling it with your money, perhaps you guys could have a decent slalom/surf boat well ahead of your Vdrive time frame.

^Please read a thread before responding. This is not being done and has been axed for some while.
If you had read it, you'd realize your post is the equivalent of yelling at the neighbors to turn down the music from their party that got canceled and never happened.

Mr. Fence and Mr, Phathom have made a wise decisions.. But there are hundreds of lurkers on here that think a prop guard will suffice..

I see these fools on our lakes..

For these types of individuals, a more graphic persuader might be required..

He's dead set on keeping the I/O until he dies. I have skied both the I/O and a direct drive. The direct drive is way nicer to ski on. We even surf a direct drive regularly with very good results.
My friend who will sell to upgrade to a v-drive actually took him out with us as a kind of sales pitch demoing all it could do towards the end of the season. The result, him saying something along the lines of, "it's a good boat and you'd be happy with it. You should buy it when you can, but you know there's always the I/O whenever you want without buying another boat."

There is something to be said about a "free" boat you can play on, but still going to be buying an inboard in the next few years to feed my surf addiction.

I'll bet that sentimental value gets a lot less valuable when someone you love or yourself cuts off a limb. Not worth it. Buy the correct equipment or don't do it. Do you use a chainsaw to hammer a nail? Probably not. Wrong tool, serious consequences can happen. Either buy a boat that's safe or use your friends. Your 70s marlin is meant for nothing even close to wake surfing.